⁠Cardiac tamponade

Overview

•Beck's triad - hypotension + raised JVP + muffled heart sounds (all three present together in only a minority of cases)

•Pulsus paradoxus - exaggerated fall in systolic BP (>10 mmHg) during normal inspiration; hallmark sign of tamponade

•Tachycardia - early compensatory response to falling stroke volume

•Hypotension - late and ominous, indicates decompensation

•Raised JVP - venous back-pressure from impaired right heart filling

•Dyspnoea - most common symptom

•Kussmaul's sign is ABSENT - JVP rises on inspiration in constrictive pericarditis but NOT in tamponade; key differentiating feature

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Pulsus paradoxus mechanism: inspiration causes right ventricle to fill preferentially; in tamponade, RV expansion shifts the interventricular septum leftwards (ventricular interdependence), reducing LV filling and stroke volume - systolic BP falls >10 mmHg. The two ventricles compete for space inside a non-compliant sac.

Investigations

•ECG - sinus tachycardia, low-voltage QRS complexes, electrical alternans (alternating QRS axis/amplitude - heart swinging in effusion)

•Chest X-ray - enlarged globular 'water bottle' cardiac silhouette; lung fields typically clear

•Echocardiography - gold standard; confirms effusion, right atrial systolic collapse, right ventricular diastolic collapse (highly specific); also guides pericardiocentesis

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Electrical alternans (beat-to-beat variation in QRS axis on ECG) is pathognomonic of a large pericardial effusion with tamponade physiology. If you see it, act immediately.

Management

•Definitive treatment: emergency pericardiocentesis (needle decompression) - drains pericardial effusion

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Avoid vasodilators, diuretics, and negative inotropes - patients are preload-dependent and compensating with tachycardia. Beta-blockers are contraindicated; reducing heart rate can precipitate cardiac arrest.

Complications